Motor protection circuit breaker — SIRIUS Size S2
The Siemens 3RV2031-4DA10-0BA0 is a SIRIUS motor protection circuit breaker, Size S2, designed for motor protection with Trip Class 10. It provides a breaking capacity of 25 kA at 400 V AC, meaning it can safely interrupt fault currents up to that level without upstream damage — critical for panel coordination in a motor branch circuit. Phase failure detection is built in, so the breaker will trip if one phase drops out, preventing single-phasing damage to the motor. Ground fault detection is not included, so a separate ground-fault relay or RCD is needed if that protection is required. Mounts via screw or snap-on onto 35 mm standard mounting rail per DIN EN 60715, in any position. The 55 mm width and 149 mm depth fit standard panel layouts — check the 10 mm side clearance and 50 mm top/bottom clearance for heat dissipation.
Breaking capacity and selectivity
Breaking capacity varies with voltage: 50 kA at 240 V AC, 50 kA at 400 V AC, 12 kA at 500 V AC, and 5 kA at 690 V AC. At 400 V, the 25 kA rating (Icu) is the standard for most industrial motor branch circuits — it coordinates with typical upstream MCCB or fuse ratings. At 690 V, the 5 kA rating is lower, so verify the available fault current at that voltage level. The closest peer in the SIRIUS family is the 3RV2023-4DA10, a Size S0 breaker. The S2 (this part) is physically larger — 55 mm wide vs. 45 mm for S0 — and offers higher breaking capacity at 400 V (25 kA vs. typically 15 kA for S0). If the panel was designed around a 3RV2023-4DA10, the S2 will not drop in without rewiring: the terminal capacity differs (M6 screws, 2x 25 mm² max), and the mounting footprint is wider. For a true form-fit-function match, stay with the same Size.
Environmental and installation limits
Operating temperature range is -50 to +60 °C, with temperature compensation active from -20 to +60 °C — the breaker adjusts its thermal trip curve across that span, so no manual derating is needed for ambient variation within that band. Storage and transport range is -50 to +80 °C. Screw-type terminals on the main circuit accept 2x 1–25 mm² or 1x 1–35 mm² solid or stranded copper. Use a Pozidriv size 2 tip with a 5–6 mm shaft diameter. The maximum switching rate at AC-3 duty is 15 operations per hour — adequate for motor starting cycles, not for high-speed jogging.